Intravascular filter retrieval device and method

ABSTRACT

A thrombus filter configured for placement in within a blood vessel lumen defined by a blood vessel wall. Methods and devices for selectively removing the thrombus filter when the presence of a filter in the vascular system is no longer desired. The thrombus filter includes a first strand formation, a second strand formation, and a joined portion.

This is a request for filing a continuation application, under 37 CFR §1.53(b), of prior application Ser. No. 09/388,563 filed on Sep. 2, 1999,now U.S. Pat. No. 6,251,122 for an invention entitled INTRAVASCULARFILTER RETRIEVAL DEVICE AND METHOD.

FIELD OF THE INVENTION

The present invention relates generally to filters for use inside bloodvessels. More particularly, the present invention relates to thrombusfilters which can be securely adjoined at a selected location in thevascular system and selectively removed when the presence of a filter inthe vascular system is no longer desired.

BACKGROUND OF THE INVENTION

There are a number of situations in the practice of medicine when itbecomes desirable for a physician to place a filter in the vascularsystem of a patient. One of the most common applications for vascularfilters is the treatment of Deep Venous Thrombosis (DVT). Deep VenousThrombosis patients experience clotting of blood in the large veins ofthe lower portions of the body. These patients are constantly at risk ofa clot breaking free and traveling via the inferior vena cava to theheart and lungs. This process is known as pulmonary embolization.Pulmonary embolization can frequently be fatal, for example when a largeblood clot interferes with the life-sustaining pumping action of theheart. If a blood clot passes through the heart it will be pumped intothe lungs and may cause a blockage in the pulmonary arteries. A blockageof this type in the lungs will interfere with the oxygenation of theblood causing shock or death.

Pulmonary embolization may be successfully prevented by the appropriateplacement of a thrombus filter in the vascular system of a patient'sbody. Placement of the filter may be accomplished by performing alaparotomy with the patient under general anesthesia. However,intravenous insertion is often the preferred method of placing athrombus filter in a patient's vascular system.

Intravenous insertion of a thrombus filter is less invasive and itrequires only a local anesthetic. In this procedure, the thrombus filteris collapsed within a delivery catheter. The delivery catheter isintroduced into the patients vascular system at a point which isconvenient to the physician. The delivery catheter is then fed furtherinto the vascular system until it reaches a desirable location forfilter placement. The thrombus filter is then released into the bloodvessel from the delivery catheter.

In the treatment of Deep Venous Thrombosis, a thrombus filter is placedin the inferior vena cava of a patient. The inferior vena cava is alarge vessel which returns blood to the heart from the lower part of thebody. The inferior vena cava may be accessed through the patient'sfemoral vein.

Thrombus filters may be placed in other locations when treating otherconditions. For example, if blood clots are expected to approach theheart and lungs from the upper portion of the body, a thrombus filtermay be positioned in the superior vena cava. The superior vena cava is alarge vessel which returns blood to the heart from the upper part of thebody. The superior vena cava may by accessed through the jugular vein,located in the patient's neck.

Once placed inside a blood vessel, a thrombus filter acts to catch andhold blood clots. The flow of blood around the captured clots allows thebody's lysing process to dissolve the clots.

SUMMARY OF THE INVENTION

The present invention pertains to thrombus filters which may be securelyadjoined at a selected location in the vascular system and selectivelyremoved when the presence of a filter in the vasculature systems is nolonger required. The present invention also pertains to devices andmethod for removing a thrombus filter using minimally invasive methods.A thrombus filter in accordance with the present invention includes afirst strand formation, a second strand formation and a joined portion.The first strand formation and the second strand formation are bothcomprised of a plurality of strands, each strand having a joined end anda free end. The joined ends of the strands are joined together proximatethe joined portion of the thrombus filter. The strands radiate away fromthe joined portion of the thrombus filter so that the first strandformation and the second strand formation are both generally conical inshape. The strands of the first strand formation and the strands of thesecond strand formation radiate in generally opposing directions.

When the thrombus filter is disposed in a blood vessel, at least one ofthe strand formations acts to trap or capture blood clots. The generallyconical shape of the strand formation serves to urge captured bloodclots toward the center of the blood flow. The flow of blood around thecaptured blood clots allows the body's natural lysing process todissolve the clots.

The free ends of the strands act as opposing wall contacting members andserve to position the thrombus filter in the center of a blood vessellumen. In a presently preferred embodiment, the strands are biased tospring outward. The radial force applied to the walls of the bloodvessel by the strand formations assists in preventing migration of thethrombus filter within the blood vessel lumen. The generally opposedorientation of the first strand formation relative to the second strandformation also makes migration of the filter less likely. Migration ofthe thrombus filter within a blood vessel lumen may also be made lesslikely by the inclusion of an anchor member proximate the free end ofeach strand.

In a presently preferred embodiment, a sliding member is disposed aboutthe joined portion of the thrombus filter. One or the other of thestrand formations may be collapsed by urging the sliding member towardthe free ends of the strands. Urging the sliding member toward the freeends of strands collapses the strand formation from a generally conicalshape to a generally cylindrical shape. Once the strand formation iscollapsed, it may be urged into the lumen of a retrieval catheter.

With one strand formation in the lumen of the retrieval catheter, theentire thrombus filter may be urged into the lumen of the retrievalcatheter. Pulling the thrombus filter in the lumen of the retrievalcatheter causes the strands of the second strand formation to collapsefrom a generally conical shape to a generally cylindrical shape. Withall strands in a collapsed position, the thrombus filter may be pulledcompletely into the lumen of the retrieval catheter. With the thrombusfilter disposed inside the lumen of the retrieval catheter, removing thethrombus filter from the body of the patient may be accomplished bywithdrawing the retrieval catheter from the blood vessel lumen.

In one embodiment of a retrieval catheter, the retrieval catheterincludes an outer tubular member, an inner tubular member and a pullingmeans. One embodiment of the pulling means includes a plurality ofretrieval struts each having a distal end. An engaging member isdisposed proximate the distal end of each strut. In one embodiment, eachengaging member includes a sharp projection. The distal ends of thestruts may be selectively urged inward so that the sharp projectionspenetrate the sliding member of the thrombus filter. Having thus coupledthe struts to the sliding member, a pulling force may be applied to thesliding member by pulling on the proximal ends of the struts.

In an additional embodiment of a retrieval catheter, the pulling meansmay include flanges fixed to the distal end of each strut. The flangesare adapted to be disposed about the fixed portion of the thrombusfilter. In a presently preferred embodiment, the joined portion of thethrombus filter has a generally cylindrical outer surface. Also, in apresently preferred embodiment, each flange includes an inner radiuswhich is substantially equal to the outer radius of the joined portionof the thrombus filter. The flanges may be selectively closed around thejoined portion of the thrombus filter. When the flanges are closedaround the joined portion of the thrombus filter, they butt against eachother to form a generally tubular shell around the joined portion of thethrombus filter.

The strands of one or the other of the strand formations may be urgedinto a collapsed position by urging the flanges toward the free ends ofthe strands. The flanges may be urged toward the free ends of thestrands by pulling on the proximal ends of the struts. Once the strandshave been moved into a collapsed position, the strand formation of thethrombus filter may be positioned within the lumen of a retrievalcatheter. This may be accomplished percutaneously by pulling on theproximal end of the struts.

With one of the strand formations positioned within the lumen of theretrieval catheter, the remainder of the thrombus filter may also beurged into the lumen of the retrieval catheter. As described previously,the strands of the second strand formation radiate away from the joinedportion of the thrombus filter in a generally opposed direction relativeto the strands of the first strand formation. The orientation of thestrands allows them to be pulled out of the walls of the blood vesselwith minimal force. The strands of the second strand formation may becollapsed by simultaneously pushing on the proximal end of the retrievalcatheter and pulling on the proximal ends of the struts.

Pulling the thrombus filter into the lumen of the retrieval cathetercauses the strands of the second formation to collapse from a generallyconical shape to a generally cylindrical shape. With all of the strandsin a collapsed position, the thrombus filter may be pulled completelyinto the lumen of the retrieval catheter. With the thrombus filterdisposed inside the lumen of the retrieval catheter, removing thethrombus filter from the body of the patient may be accomplished bywithdrawing the retrieval catheter from the blood vessel lumen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a thrombus filter positioned in the lumen of ablood vessel lumen;

FIG. 2 is a plan view of a removal catheter disposed in a blood vessellumen proximate the thrombus filter of FIG. 1;

FIG. 3 is a plan view of an alternate embodiment of a thrombus filterand a removal catheter positioned in the lumen of a blood vessel lumen;

FIG. 4 is a plan view of the thrombus filter of FIG. 3 illustrating analternate method of removal; and

FIG. 5 is a plan view of an alternate embodiment of a thrombus filterand removal catheter.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description should be read with reference to thedrawings, in which like elements in different drawings are numberedidentically. The drawings which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention.

Examples of constructions, materials, dimensions, and manufacturingprocesses are provided for selected elements. All other elements employthat which is known to those of skill in the field of the invention.Those skilled in the art will recognize that many of the examplesprovided have suitable alternatives which may be utilized.

Reference is now made to the drawings, in which like numbers refer tolike elements throughout. FIG. 1 is a plan view of a thrombus filter 20positioned in a lumen 22 of a blood vessel 24. Blood vessel 24 includeswalls 26 which define lumen 22. The main components of thrombus filter20 are a first strand formation 30, second strand formation 40, and ajoined portion 50.

First strand formation 30 and second strand formation 40 are bothcomprised of a plurality of strands 32 and 42 respectively. Each strand32 of first strand formation 30 has a joined end 34 and a free end 36.Likewise, each strand 42 of second strand formation 40 has a joined end44 and a free end 46. Joined ends 34 of strands 32 and joined ends 44 ofstrands 42 are joined at joined portion 50 of thrombus filter 20.

Strands 32 radiate away from joined portion 50 of thrombus filter 20 sothat first strand formation 30 is generally conical in shape. Likewise,strands 42 radiate away from joined portion 50 of the thrombus filter 20such that second strand formation 40 is generally conical in shape. Asshown in FIG. 1, strands 32 of first strand formation 30 and strands 42of second strand formation 40 radiate in generally opposing directions.

When thrombus filter 20 is disposed in a blood vessel, at least one ofthe strand formations acts to trap, or capture blood clots. Thegenerally conical shape the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

Strands 32 and 42 act as opposing wall contacting members and serve toposition thrombus filter 20 in the center of lumen 22 of blood vessel24. In a presently preferred embodiment, strands 32 and 42 are biased tospring outward. The radial force applied to the walls of the bloodvessel by first strand formation 30 and second strand formation 40assists in preventing migration of thrombus filter 20 within bloodvessel lumen 22. The generally opposed orientation of strands 42relative to strands 32 also makes migration of the filter less likely.

Migration of filter 20 within blood vessel lumen 22 may also made lesslikely by the inclusion of anchors on thrombus filter 20. An anchor 62is disposed at free end 46 of each strand 42. Likewise, each free end 36of each strand 32 includes an anchor 60. In FIG. 1, anchors 60 and 62are pictured as sharp projections or barbs. It should be understood thatanchors 60 and 62 may be comprised of other means for anchoring withoutdeparting from the spirit or scope of this invention. It should also beunderstood that embodiments of thrombus filter 20 which include noanchors are possible without departing from the spirit or scope of thepresent invention.

In the embodiment of FIG. 1, joined portion 50 includes a collar 52disposed about joined ends 34 of strands 32 and joined ends 44 ofstrands 42. A sliding member 70 is disposed about joined portion 50. Inthe embodiment of FIG. 2 sliding member 70 is preferably comprised of aplastic material. Examples of suitable plastic materials includepolyethylene (PE), polypropylene (PP), thermoset polyurethane,thermoplastic polyurethane, and polyether block amide (PEBA). Those withskill in the art will appreciate that sliding member 70 may be comprisedof other materials without deviating from the spirit or scope of thepresent invention. A ring 54 is fixed to joined portion 50 proximate oneend of sliding member 70. Ring 54 may act as a stop to limit the travelof sliding member 70.

Although two strands 32 and two strands 34 are shown in FIG. 1. Anynumber of strands 32, 34 may be used. In a presently preferredembodiment first strand formation 30 includes between about 3 strands 32and about 6 strands 32. In a presently preferred embodiment secondstrand formation 40 includes between about 3 strands 42 and about 6strands 42.

In a presently preferred embodiment, strands 32, 42 are generallycircular in cross section, it should be understood that othercross-sectional shapes are possible without deviating from the spirit orscope of the invention. For example, the cross-sectional shape ofstrands 32, 42 may be circular, rectangular, square, triangular, oval,etc.

In a presently preferred embodiment, strands 32, 42 are comprised ofnickel-titanium alloy. Suitable nickel-titanium alloys are commerciallyavailable from Memry Technologies (Brookfield, Conn.), TiNi AlloyCompany (San Leandro, Calif.), and Shape Memory Applications (Sunnyvale,Calif.).

Those with skill in the art will appreciate that strands 32, 42 may becomprised of other metallic or non-metallic materials without departingfrom the spirit or scope of the present invention. Examples of metallicmaterials which may be suitable for some applications include stainlesssteel and titanium. Suitable, non-metallic materials may be selectedfrom the following list, which is not exhaustive: poly(L-lactide)(PLLA), poly(D,L-lactide) (PLA), polyglycolide (PGA),poly(L-lactide-co-D,L-lactide) (PLLA/PLA), poly(L-lactide-co-glycolide)(PLLA/PGA), poly(D,L-lactide-co-glycolide) (PLA/PGA),poly(glycolide-co-trimethylene carbonate) (PGA/PTMC), polyethylene oxide(PEO), polydioxanone (PDS), polycaprolactone (PCL), polyhydroxylbutyrate(PHBT), poly(phosphazene), polyD,L-lactide-co-caprolactone) (PLA/PCL),poly(glycolide-co-caprolactone) (PGA/PCL), polyanhydrides (PAN),poly(ortho esters), poly(phoshate ester), poly(amino acid), poly(hydroxybutyrate), polyacrylate, polyacrylamid, poly(hydroxyethyl methacrylate),polyurethane, polysiloxane and their copolymers.

FIG. 2 is a plan view of a removal catheter 90 disposed in blood vessellumen 22 proximate thrombus filter 20. Removal catheter 90 includes anouter tubular member 100 having a lumen 102, a distal end 104, and aproximal end 106 (not shown).

In the embodiment of FIG. 2, an inner tubular member 200 is disposedwithin lumen 102 of outer tubular member 100. Inner tubular member 200includes a lumen 202, a distal end 204, and a proximal end 206 (notshown). An elongate shaft 210 and a pulling means 300 are disposedwithin lumen 202 of inner tubular member 200.

Pulling means 300 includes a plurality of retrieval struts 302 eachhaving a distal end 304, a proximal end 306 (not shown), and a distalportion 308. An engaging member 310 is disposed proximate the distal end304 of each strut 302. In the embodiment of FIG. 2, each engaging member310 includes a sharp projection 312.

In the embodiment of FIG. 2, distal portions 308 of retrieval struts 302are biased to spring outward. Distal portions 308 of retrieval struts302 may be selectively urged inward by urging distal end 204 of innertubular member 200 toward distal ends 304 of retrieval struts 302.During a surgical procedure, this may be accomplished percutaneously bypushing on proximal end 206 (not shown) of inner tubular member 200,and/or pulling on proximal ends 306 (not shown) of retrieval struts 302.

A method of removing thrombus filter 20 from blood vessel lumen 22 maynow be described with reference to FIG. 2. The retrieval processtypically begins by introducing catheter 90 into the patients vascularsystem. The retrieval catheter typically enters the patients vascularsystem at a point which is readily accessible to the physician. Once inthe vascular system, the retrieval catheter is urged forward untildistal end 104 of outer tubular member 100 is proximate thrombus filter20.

For example, if thrombus filter 20 is located in the inferior vena cavaof a patient's vascular system, removal catheter 90 may enter thevascular system at the femoral vein. Alternately, if thrombus filter 20is located in the superior vena cava of a patient's vascular system,removal catheter 90 may enter the vascular system at the jugular vein.In either case, the filter removal procedure is minimally invasive, andgenerally does not require general anesthesia.

Preferably, distal portions 308 of retrieval struts 302 will be in aretracted position while the distal end of retrieval catheter 90 isadvanced through the vasculature. Distal portions 308 may be held in aretracted position by inner tubular member 200. When the distal end ofcatheter 90 is proximate thrombus filter 20 inner tubular member 200 maybe pulled back, allowing distal portions 308 of struts 302 to springoutward. Struts 302 may then be urged forward until distal ends 304 ofstruts 302 are proximate slide 70 of thrombus filter 20.

Distal portions 308 of struts 302 may then be urged towards slide 70 byurging distal end 204 of inner tubular member 200 toward distal ends 304of struts 302. This may be accomplished percutaneously by simultaneouslypushing on distal end 206 of inner tubular member 200 and pulling ondistal ends 306 of struts 302. When distal portions 308 of struts 302are closed onto slide 70, sharp projections 312 penetrate into slide 70.

A pulling force may then be applied to slide 70. In a presentlypreferred embodiment, this pulling force is created by pulling onproximal ends 306 of struts 302. Also in a presently preferredembodiment, thrombus filter 20 may be held in position by pushing thedistal end of elongate shaft 210 against thrombus filter 20.

Strands 32 may be urged into a collapsed position by urging slide 70toward free ends 36 of strands 32. Once strands 32 have been moved to acollapsed position, first strand portion 30 of thrombus filter 20 may bepositioned within lumen 102 of outer tubular member 100. This may beaccomplished percutaneously by pushing on proximal end 106 of outertubular member 100 and/or pulling on proximal ends 306 of struts 302.

Once first strand formation 30 is positioned within lumen 102 of outertubular member 100, the remainder of thrombus filter 20 may also beurged into lumen 102 of outer tubular member 100. As describedpreviously, strands 42 of second strand formation 40 radiate away fromjoined portion 50 of thrombus filter 20 in a generally opposed directionrelative to strands 32 of first strand formation 30. The orientation ofstrands 42 allows them to be pulled out of walls 26 of blood vessel 22with minimal force. Strands 42 may be converted to a collapsed positionby simultaneously by pushing on proximal end 106 of outer tubular member100 and pulling on proximal ends 306 of struts 302.

Pulling thrombus filter 20 into lumen 102 of outer tubular member 100causes strands 42 to collapse causing second strand formation 40 totransform from a generally conical shape to a generally cylindricalshape. With strands 32 and strands 42 in a collapsed position, thrombusfilter 20 may be pulled completely into lumen 102 of outer tubularmember 100. With thrombus filter 20 disposed inside lumen 102 of outertubular member 100, removing thrombus filter 20 from the body of thepatient may be accomplished by withdrawing retrieval catheter 90 fromblood vessel lumen 22.

FIG. 3 is a plan view of an alternate embodiment of thrombus filter 20positioned in a lumen 22 of a blood vessel 24. Blood vessel 24 includeswalls 26 which define lumen 22. The main components of thrombus filter20 are a first strand formation 30, second strand formation 40, and ajoined portion 50.

First strand formation 30 and second strand formation 40 are bothcomprised of a plurality of strands 32 and 42 respectively. Each strand32 of first strand formation 30 has a joined end 34 and a free end 36.Likewise, each strand 42 of second strand formation 40 has a joined end44 and a free end 46. Joined ends 34 of strands 32 and joined ends 44 ofstrands 42 are joined at joined portion 50 of thrombus filter 20. In theembodiment of FIG. 3, joined portion 50 includes solder 56. Solder 56 isused to fix joined ends 34 of strands 32 and joined ends 44 of strands42 together. Other methods may be used to fix joined ends 34, 44 ofstrands 32, 42 without departing from the spirit or scope of the presentinvention. For example, brazing, welding, mechanical fasteners, and theuse of adhesives may be suitable for some applications.

Strands 32 radiate away from joined portion 50 of thrombus filter 20 sothat first strand formation 30 is generally conical in shape. Likewise,strands 42 radiate away from joined portion 50 of the thrombus filter 20such that second strand formation 40 is generally conical in shape. Asshown in FIG. 1, strands 32 of first strand formation 30 and strands 42of second strand formation 40 radiate in generally opposing directions.

When thrombus filter 20 is disposed in a blood vessel, at least one ofthe strand formations acts to trap, or capture blood clots. Thegenerally conical shape the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

Strands 32 and 42 act as opposing wall contacting members and serve toposition thrombus filter 20 in the center of lumen 22 of blood vessel24. In a presently preferred embodiment, strands 32 and 42 are biased tospring outward. The radial force applied to the walls of the bloodvessel by first strand formation 30 and second strand formation 40assists in preventing migration of thrombus filter 20 within bloodvessel lumen 22. The generally opposed orientation of strands 42relative to strands 32 also makes migration of the filter less likely.

Migration of filter 20 within blood vessel lumen 22 may also made lesslikely by the inclusion of anchors on thrombus filter 20. An anchor 62is disposed at free end 46 of each strand 42. Likewise, each free end 36of each strand 32 includes an anchor 60. In FIG. 1, anchors 60 and 62are pictured as sharp projections or barbs. It should be understood thatanchors 60 and 62 may be comprised of other means for anchoring withoutdeparting from the spirit or scope of this invention. It should also beunderstood that embodiments of thrombus filter 20 which include noanchors are possible without departing from the spirit or scope of thepresent invention.

Two slides 72 and 74 are disposed about joined portion 50. In theembodiment of FIG. 3 each sliding member 70, 74 is comprised of ahelical coil. The strength of slides 72, 74 may be increased bysoldering or otherwise bonding consecutive turns of the helical coil toeach other. In FIG. 3, slide 74 is shown in partial cross section.Slides 72, 74 include coupling members 76, 78 respectively.

In FIG. 3, a removal catheter 400 is disposed in lumen 22 of bloodvessel 24. Removal catheter 400 includes a lumen 402, a distal end 404,and a proximal end 406 (not shown). An elongate member 500 is disposedin lumen 402 of removal catheter 400. Elongate member 500 includes adistal end 504, a proximal end 506 (not shown), and a coupling member502 disposed proximate distal end 504.

A method of removing thrombus filter 20 from blood vessel lumen 22 maynow be described with reference to FIG. 3. The retrieval processtypically begins by introducing the catheter into the patients vascularsystem. The retrieval catheter typically enters the patients vascularsystem at a point which is readily accessible to the physician. Once inthe vascular system, the retrieval catheter is urged forward untildistal end 404 is proximate thrombus filter 20.

For example, if thrombus filter 20 is located in the inferior vena cavaof a patient's vascular system, removal catheter 400 may enter thevascular system at the femoral vein. Alternately, if thrombus filter 20is located in the superior vena cava of a patient's vascular system,removal catheter 400 may enter the vascular system at the jugular vein.In either case, the filter removal procedure is minimally invasive, andgenerally does not require general anesthesia.

The retrieval catheter is advanced through blood vessel lumen 22 untildistal end 404 catheter 400 is proximate thrombus filter 20. Distal end504 of elongate member 500 is then coupled to sliding member 72. Thismay be accomplished by mating coupling member 502 of elongate member 500with coupling member 76 of the sliding member 72. A pulling force isthen applied to sliding member 72. In a presently preferred embodiment,this pulling force is created by pulling on proximal end 506 (not shown)of elongate member 500.

Pulling on sliding member 72 urges sliding member 72 toward free ends 36of strands 32. As sliding member 72 moves, it causes strands 32 tocollapse. Once strands 32 move to a collapsed position, first strandformation 30 of thrombus filter 20 may be urged into lumen 402 ofretrieval catheter 400.

Once first strand formation 30 has entered lumen 402 of retrievalcatheter 400, thrombus filter 20 may be urged further into lumen 402 ofcatheter 400. As described previously, strands 42 of second strandformation 40 radiate away from joined portion 50 of thrombus filter 20in a generally opposed direction relative to strands 32 of first strandformation 30. The orientation of strands 42 allows them to be pulledaway from walls 26 of blood vessel 24 with minimal force.

Pulling thrombus filter 20 into lumen 402 of retrieval catheter 400causes strands 42 to collapse causing second strand formation 40 totransform from a generally conical shape to a generally cylindricalshape. The collapse of strands 32 and 42 allows all of thrombus filter20 to be disposed in lumen 402 of catheter 400. With thrombus filter 20disposed inside lumen 402 of retrieval catheter 400, removing thrombusfilter 20 from the body of the patient may be accomplished bywithdrawing retrieval catheter 400 from blood vessel lumen 22.

An additional method of removing thrombus filter 20 from blood vessellumen 22 has been envisioned in which two removal catheters 400A and400B are utilized. This method may be described with reference to FIG.4.

The retrieval process typically begins by introducing catheters 400A,400B into the patients vascular system. Once in the vascular system,retrieval catheters 400A, 400B are urged forward until distal ends 404A,404B are proximate thrombus filter 20.

Retrieval catheters 400A, 400B enter the patient's vascular system atpoints which allow them to approach thrombus filter 20 fromsubstantially opposing directions. For example, removal catheter 400Amay enter the vascular system at the femoral vein and removal catheter400B may enter the vascular system at the patients right internaljugular vein.

Retrieval catheter 400A is advanced through the vasculature of thepatient until distal end 404A of catheter 400A is proximate first strandformation 30 of thrombus filter 20. Likewise, retrieval catheter 400B isadvanced through the vasculature of the patient until distal end 404A ofcatheter 400B is proximate second strand formation 40 of thrombus filter20.

Distal end 504A of elongate member 500A is then coupled to slidingmember 72. This may be accomplished by mating coupling member 502A ofelongate member 500A with coupling member 76 of the sliding member 72.Likewise, distal end 504B of elongate member 500B is coupled to slidingmember 74. This may be accomplished by mating coupling member 502B ofelongate member 500B with coupling member 78 of the sliding member 74.

Sliding member 72 may now be urged towards distal ends 36 of strands 32by applying a pulling force to proximal end 506A (not shown) of elongatemember 500A. Simultaneously, sliding member 74 may now be urged towardsdistal ends 46 of strands 42 by applying a pulling force to proximal end506B (not shown) of elongate member 500B.

Urging sliding member 72 toward free ends 36 of strands 32 causes firststrand formation 30 to collapse. Likewise, urging sliding member 74toward free ends 46 of strands 42 causes second strand formation 40 tocollapse.

Once strands 32, 42 move to a collapsed position, thrombus filter 20 maybe urged into lumen 402A of retrieval catheter 400A. Alternately,thrombus filter 20 may be pulled into lumen 402B of retrieval catheter400B. With thrombus filter 20 disposed inside the lumen of a ofretrieval catheter, removing thrombus filter 20 from the body of thepatient may be accomplished by withdrawing the retrieval catheter fromblood vessel lumen 22.

Other embodiments have been envisioned. For example, sliding member 72and sliding member 74 may be replaced with one sliding member comprisedof a continuous helical coil. In this embodiment, pulling in opposingdirections on coupling members 76, 78 would cause the helical coil toexpand in length.

FIG. 5 is a plan view of an alternate embodiment of thrombus filter 20positioned in a lumen 22 of a blood vessel 24. Blood vessel 24 includeswalls 26 which define lumen 22. The main components of thrombus filter20 are a first strand formation 30, second strand formation 40, and ajoined portion 50.

First strand formation 30 and second strand formation 40 are bothcomprised of a plurality of strands 32 and 42 respectively. Each strand32 of first strand formation 30 has a joined end 34 and a free end 36.Likewise, each strand 42 of second strand formation 40 has a joined end44 and a free end 46. Joined ends 34 of strands 32 and joined ends 44 ofstrands 42 are joined at joined portion 50 of thrombus filter 20. In theembodiment of FIG. 5, joined portion 50 includes a collar 52 disposedabout joined ends 34, 44 of strands 32, 42.

Strands 32 radiate away from joined portion 50 of thrombus filter 20 sothat first strand formation 30 is generally conical in shape. Likewise,strands 42 radiate away from joined portion 50 of the thrombus filter 20such that second strand formation 40 is generally conical in shape. Asshown in FIG. 5, strands 32 of first strand formation 30 and strands 42of second strand formation 40 radiate in generally opposing directions.

When thrombus filter 20 is disposed in blood vessel lumen 22, at leastone of the strand formations acts to trap, or capture blood clots. Thegenerally conical shape the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

Strands 32 and 42 act as opposing wall contacting members and serve toposition thrombus filter 20 in the center of lumen 22 of blood vessel24. In a presently preferred embodiment, strands 32 and 42 are biased tospring outward. The radial force applied to the walls of the bloodvessel by first strand formation 30 and second strand formation 40assists in preventing migration of thrombus filter 20 within bloodvessel lumen 22. The generally opposed orientation of strands 42relative to strands 32 also makes migration of the filter less likely.

Migration of filter 20 within blood vessel lumen 22 may also made lesslikely by the inclusion of anchors on thrombus filter 20. An anchor 62is disposed at free end 46 of each strand 42. Likewise, each free end 36of each strand 32 includes an anchor 60. In FIG. 5, anchors 60 and 62are pictured as sharp projections or barbs. It should be understood thatanchors 60 and 62 may be comprised of other means for anchoring withoutdeparting from the spirit or scope of this invention. It should also beunderstood that embodiments of thrombus filter 20 which include noanchors are possible without departing from the spirit or scope of thepresent invention.

FIG. 5 includes a removal catheter 590 disposed in blood vessel lumen 22proximate thrombus filter 20. Removal catheter 590 includes an outertubular member 600 having a lumen 602, a distal end 604, and a proximalend 606 (not shown).

In the embodiment of FIG. 5, an inner tubular member 700 is disposedwithin lumen 602 of outer tubular member 600. Inner tubular member 700includes a lumen 702, a distal end 704, and a proximal end 706 (notshown). An elongate shaft 710 and a pulling means 800 are disposedwithin lumen 702 of inner tubular member 700.

Pulling means 800 includes a plurality of struts 802 each having adistal end 804, a proximal end 806 (not shown), and a distal portion808. An engaging member 810 is disposed proximate the distal end 804 ofeach strut 802. In the embodiment of FIG. 5, each engaging member 810includes a flange 812. Flanges 812 are adapted to be disposed aboutcollar 52 of thrombus filter 20. In a presently preferred embodiment,collar 52 has a generally cylindrical outer surface. Also in a presentlypreferred embodiment each flange 812 includes an inner radius which issubstantially equal to the outer radius of collar 52. When flanges 812are closed around collar 52 they butt against each other to form agenerally tubular shell around collar 52.

In the embodiment of FIG. 5, distal portions 808 of retrieval struts 802are biased to spring outward. Distal portions 808 of retrieval struts802 may be selectively urged inward by urging distal end 704 of innertubular member 700 toward distal ends 804 of retrieval struts 802.During a surgical procedure, this may be accomplished percutaneously bypushing on proximal end 706 (not shown) of inner tubular member 700,and/or pulling on proximal ends 806 (not shown) of retrieval struts 802.

A method of removing thrombus filter 20 from blood vessel lumen 22 maynow be described with reference to FIG. 5. The retrieval processtypically begins by introducing catheter 590 into the patients vascularsystem. Once in the vascular system, the retrieval catheter is urgedforward until distal end 604 of outer tubular member 600 is proximatethrombus filter 20.

Preferably, distal portions 808 of retrieval struts 802 will be in aretracted position while the distal end of retrieval catheter 590 isadvanced through the vasculature. Distal portions 808 may be held in aretracted position by inner tubular member 700.

When the distal end of catheter 590 is proximate thrombus filter 20inner tubular member 700 may be pulled back, allowing distal portions808 of struts 802 to spring outward. Struts 802 may then be urgedforward until distal ends 804 of struts 802 are proximate joined portion50 of thrombus filter 20.

Distal portions 808 of struts 802 may then be urged towards joinedportion 50 by urging distal end 604 of inner tubular member 700 towarddistal ends 804 of struts 802. This may be accomplished percutaneouslyby simultaneously pushing on distal end 706 (not shown) of inner tubularmember 700 and pulling on distal ends 806 of struts 802. When distalportions 808 of struts 802 are closed onto joined portion 50, flanges812 close around collar 52. Flanges 812 are adapted so that they butttogether and form a substantially tubular shell around collar 52.

Strands 32 may be urged into a collapsed position by urging flanges 812toward free ends 36 of strands 32. Flanges 812 may be urged toward freeends 36 of strands 32 by pulling on proximal ends 806 of struts 802. Ina presently preferred method, thrombus filter 20 may be held in positionby pushing the distal end of elongate shaft 710 against thrombus filter20. Once strands 32 have been moved to a collapsed position, firststrand portion 30 of thrombus filter 20 may be positioned within lumen602 of outer tubular member 600. This may be accomplished percutaneouslyby pushing on proximal end 606 of outer tubular member 600 and/orpulling on proximal ends 806 of struts 802.

Once first strand formation 30 is positioned within lumen 602 of outertubular member 600, the remainder of thrombus filter 20 may also beurged into lumen 602 of outer tubular member 600. As describedpreviously, strands 42 of second strand formation 40 radiate away fromjoined portion 50 of thrombus filter 20 in a generally opposed directionrelative to strands 32 of first strand formation 30. The orientation ofstrands 42 allows them to be pulled out of walls 26 of blood vessel 22with minimal force. Strands 42 may be converted to a collapsed positionby simultaneously by pushing on proximal end 606 of outer tubular member600 and pulling on proximal ends 806 of struts 802.

Pulling thrombus filter 20 into lumen 602 of outer tubular member 600causes strands 42 to collapse causing second strand formation 40 totransform from a generally conical shape to a generally cylindricalshape. With strands 32 and strands 42 in a collapsed position, thrombusfilter 20 may be pulled completely into lumen 602 of outer tubularmember 600. With thrombus filter 20 disposed inside lumen 602 of outertubular member 600, removing thrombus filter 20 from the body of thepatient may be accomplished by withdrawing retrieval catheter 590 fromblood vessel lumen 22.

Numerous advantages of the invention covered by this document have beenset forth in the foregoing description. It will be understood, however,that this disclosure is, in many respects, only illustrative. Changesmay be made in details, particularly in matters of shape, size, andarrangement of parts without exceeding the scope of the invention. Theinventions's scope is, of course, defined in the language in which theappended claims are expressed.

What is claimed is:
 1. A retrieval catheter comprising: an outer tubularmember having a first lumen, a distal end, and a proximal end; an innertubular member having a second lumen, a distal end, and a proximal end,the inner tubular member being slidingly disposed within the lumen ofthe outer tubular member; and means for pulling a filter, including aplurality of retrieval struts each having a distal end, a proximal end,and a distal portion including an engaging member, wherein the pluralityof retrieval struts are disposed within the lumen of the inner tubularmember.
 2. The retrieval catheter of claim 1 wherein each engagingmember comprises a sharp projection.
 3. The retrieval catheter of claim2 wherein each strut is aligned so that the sharp projection of theengaging member of each strut points inward with respect to theplurality of struts.
 4. The retrieval catheter of claim 1 wherein eachengaging member comprises a flange.
 5. The retrieval catheter of claim 4wherein the flanges, when compressed together, abut against one anotherto form a tubular member.
 6. The retrieval catheter of claim 1 furthercomprising an elongate shaft.
 7. The retrieval catheter of claim 6wherein the elongate shaft is disposed within the lumen of the innertubular member.
 8. The retrieval catheter of claim 6 wherein theelongate shaft is disposed outside the inner tubular member.
 9. Theretrieval catheter of claim 6 wherein the elongate shaft is slidinglydisposed within the lumen of the inner tubular member.
 10. The retrievalcatheter of claim 6 wherein the elongate shaft can be accessed from alocation proximate the proximal end of the retrieval catheter while thedistal end of the elongate shaft is proximate the distal end of theretrieval catheter.
 11. The retrieval catheter of claim 6 wherein theelongate shaft can be accessed from a location proximate the proximalend of the retrieval catheter while the distal end of the elongate shaftextends beyond the distal end of the retrieval catheter.
 12. Theretrieval catheter of claim 6 wherein the elongate shaft extends from alocation proximate the proximal end of the retrieval catheter to alocation proximate the distal end of the retrieval catheter.